Equinox, which is the largest ­Australian-listed pure-play copper miner, has been examining a $350 million expansion from its processing capacity of up to 24 million tonnes of ore annually to 35 million tonnes.

But it pleased the market yesterday by saying the scope of the study had been broadened to include “a number of additional scenarios" that would allow it to process up to 45 million tonnes of material a year to produce more than 300,000 tonnes of copper.

That would boost future production 29 per cent beyond the market’s expectation for the expansion, at a time when there is a heightened focus on future copper supply.

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Copper is trading at near record highs of about $US4.27 a pound. Credit Suisse is forecasting a peak price of $US5 a pound in the fourth quarter of this year and the first quarter of 2012. It has also boosted its long-term price forecast to $US2.50 a pound from $US2.

Equinox is understood to be considering the larger expansion because of encouraging signs there are more copper resources on its tenements than previously thought.

A feasibility study on the expansion options being run by Ausenco is under way and should be complete during the second quarter this year, but it would essentially involve duplicating the existing processing facilities at the mine site.

Equinox has estimated it will take three to five years to complete the expansion.

Equinox produced 33,939 tonnes of copper in the fourth quarter despite mining lower grades than previously. That allowed it to exceed its guidance of 140,000 tonnes of annual production.

In addition to the copper mined, Equinox mined and stockpiled a small amount of uranium ore during the period, which has been expensed as waste.

The miner has been considering whether to add a uranium processing plant to its operation after deferring the project during the global financial crisis.

Equinox completed a $1.2 billion acquisition of Citadel Resource Group last week, which has given it control of the Jabil Sayid copper mine under development in Saudi Arabia. However, Jabil Sayid is not expected to contribute any production until early next year.